The present invention relates generally to a sheet product dispenser, and in particular to a sheet product dispenser that provides for the detecting of sheet product and for the loading of sheet product for dispensing.
Sheet product dispensers typically include multiple rolls of sheet product. The sheet product dispensers are typically arranged to allow maintenance personnel to utilize a partially depleted roll sometimes referred to as a “stub roll.” This partially depleted or stub roll is usually placed in a position to dispense sheet product first to maximize the utilization of sheet product and minimize waste. A second roll, usually a full roll, is also placed within the sheet product dispenser to be used once the stub roll has been depleted.
While some sheet product dispensers merely store the full roll for later manual refilling by maintenance personnel, it generally preferred to have the secondary roll automatically dispense once the stub roll is depleted. The automatic dispensing of the secondary roll allows the operator of the dispenser is located to increase the time period between maintenance personnel visits, thus decreasing operating costs and minimizing waste. Sheet product is generally dispensed using a roller system where the sheet product is passed between two rollers and the resulting friction pulls the sheet product from the dispensing roll.
The switch from the stub roll to the secondary roll may be accomplished using a bar that pushes the end of the secondary roll of sheet product into the rollers. Once the sheet product of the secondary roll has been positioned against the rollers, the resulting friction pulls the sheet product through the rollers and is thereafter dispensed to the user. It is desirable to minimize waste in the operation of the sheet product dispenser to minimize costs. However, it is also desirable to have sheet product available when the user activates the sheet product dispenser. These requirements have led to a variety of sheet dispensing mechanisms that try to balance these somewhat conflicting demands.
One category of sensing mechanisms used some type of mechanical lever that rested against the outer diameter of the stub roll to measure the amount of remaining sheet product. At a certain point, the diameter of the stub roll was small enough such that the lever activated the transfer mechanism allowing the sheet product from the secondary roll to be dispensed. While these mechanical systems worked well, due to the imprecise nature of detecting the diameter of the stub roll using a mechanical lever, the system inevitably needed to be set to have the secondary roll dispense prior to complete depletion of the stub roll. When this occurred, sheet product from both sheets was dispensed when the sheet product dispenser was activated. While this arrangement ensured that the user received sheet product, it also resulted in wasted sheet product and increased costs.
A second category of sensing mechanisms utilized a sensor positioned within a dispensing chute of the sheet product dispenser. The dispensing chute is an area adjacent an opening in the sheet product dispenser where the sheet product exits and is retrieved by the user. The sensor was coupled to a microprocessor that controls the operation of the sheet product dispenser. These sensors are arranged to detect the front edge of the sheet product or its absence. The microprocessor used edge detection to ensure that perforations in the sheet product were appropriately positioned at the end of a dispense cycle to allow the sheet product to be torn by an end user.
This second category of sheet product dispensers also typically had two motors. A drive motor operates the rollers to dispense sheet product as discussed above, and a transfer motor that activates a transfer bar to transfer sheet product from the secondary roll. The transfer motor is coupled to the transfer bar via a series of linkages that translate the rotational movement of the motor into a linear translation of the transfer bar. While this arrangement allowed for the automatic dispensing of sheet product from the second roll, several issues resulted. First, the use of the sensor in the chute limited the usage to sheet product having perforations since the tearing movement (through use of a tear bar for example) required for non-perforated sheet product could cause false signals to be generated by the sensor. Second, since the sensor detected the front edge of the sheet product, a short period of time would elapse before the rear edge of sheet product from the stub roll would pass the sensor and trigger the transfer mechanism. Thus there could be a considerable gap in the dispensing of sheet product while the sheet product dispenser triggered the transfer motor and transfer bar.
While existing sheet product dispensers are suitable for their intended purposes, there still remains a need for improvements particularly regarding the detecting when the sheet product on a stub roll has been depleted. There is also a need for improvements that minimize waste while providing consistent dispensing of sheet product for an end user. There is also a need to better detect a user's presence while conserving battery power. Further, there is a need to minimize noise generated by the sheet product dispenser.